Bass line patch played by a bass player

[fla_2000]

Hi guys. Sorry for my english
My bass player in my band doesn't Have a good sound of synth bass so i thought to create a patch on my nord modular G2 and connecting the bass on nord modular external audio input in order that the bass audio signal play the synthesizer.
I created this patch using the "2 in" module linked to "pitch tracker" module and to "envelope followers" module. The First One goes to pitch input of the oscillators and the second one to filter modulation input.
The problem Is that the sound Is very bad. Oscillators pitch seems tò be modulated by the audio signal in a strange way and the result Is similar to osc pitch modulated by noise.
What does It go wrong? In your opinion Is It possible to create a good patch played by and Ext audio signal or not?
If yes what Is the mistake? Thanks